Theory
j bryan's post in which he included average HP over an RPM range with MEVI and USIM compared got me thinking, what does it do in the RPM range used mostly when drag racing? So I dusted off the dyno plots and decided to do a little math.

Calculations
I used the 2/3 shift as the basis for my comparison. To put things on a level playing field, I calculated the RPM drop shifting from 2nd to 3rd gear. For this shift, the RPMs drop about 31%. Thus I came up with an RPM range over which to calculate average HP of 4000RPM-5800RPM for the USIM, and 4350RPM-6300RPM for the MEVI*.

*Disclaimer-my dyno plots end at 6400RPM but the HP is already dropping due to fuel cutoff at 6400RPM. I stopped calculating avg HP for MEVI dyno run at 6300.

After a few minutes of plugging and chugging I came up with the following figures for average HP over the typical drag racing range:

USIM: 166.60 average HP over 4000-5800RPM
MEVI: 167.26 average HP over 4350-6300RPM
Advantage MEVI by 0.66 HP (Why'd I spend $650 on this again? Read on...)

Extrapolation
Let's say for the sake of comparison that one has a JWT ECU and the true redline is extended out to 7000RPM. Let's be conservative and say that the JWT provides no power gains of any sort, and ONLY increases the redline out to 7000RPM. Using the 31% RPM drop from 2nd to 3rd gear, this would result in entering 3rd gear at ~4850RPM. Also let's assume that my HP figures at 6300RPM stay that way, not losing or gaining, out to 7000RPM... where would this put us for average HP over the used RPM range?

MEVI + JWT ECU: 176.23* average HP over 4850-7000RPM.

*Disclaimer-remember this was assuming a number of things, one that JWT ECU gains no HP at all, and that the 6300rpm plateau is continued all the way out to 7000RPM.

Conclusion
On on the surface, the gains of the MEVI without JWT ECU seem to be not worth the money. One must remember however that allowing the car to make the SAME AVERAGE HP but in a HIGHER RPM RANGE means you can stay in each gear longer. I'd rather be in 3rd gear at 95mph making 181whp than having already shifted into 4th and only be making 168whp at 95mph (and not accelerating as quickly).

Also, this comparison was done using the 2nd/3rd gear reference in order to remove the variability of the launch. One might say "but the launch is the most critical part of the race and thats where the MEVI sucks!" This is true, however, in a drag race situation on street tires, in 1st gear you are usually spinning the tires to one extent or another so WHO KNOWS how much HP/TQ is actually being transferred to the ground to accelerate the car. The coefficient of friction between the tires and the track surface can only handle X amount of torque load, and regardless of whether or not you have the MEVI, you are putting down more torque than the tires can handle, and overwhelm them into spinning.

So, what have we learned? USIM and MEVI put down almost identical HP to the ground in a drag racing situation, but the ability of the MEVI to extend this average hp into the upper reaches of the RPM range is beneficial as you can stay in each gear longer, and most likely also avoid having to make that pesky 3rd-4th shift right before the finish line, improving your ET further.

My dragstrip times:

Best with MEVI (street tires) 14.45 @ 96.7mph
Best with USIM (street tires) 14.41 @ 96.6.

However ON THE AVERAGE, my ETs improved .11 seconds and my trap speeds improved 1.4mph (street tires) comparing the runs I made before the MEVI to after the MEVI (all other mods/preparations being the same).

Take from this what you will.

 

Okay..so 1/4 times/trapspeeds may be similar (gotta remember that not everyone cares about drag racing or stoplight racing)...but what about freeway speeds? I'd think a VI 4th gen will easily take it's non-VI counterpart at higher speeds (say 60mph+ rollon).

Also, perhaps it'd help more for autos than 5-speeds...

 

Interesting. Good info Neal. I know there is a few unknown or unused factors but it still gives a good idea what the VI and 7000rpm rev limiter will do for us.
Do you know or have you seen info on what gains are seen from the JWT ECU besides the raised rev limiter?? If so, where in the powerband are they seen??

VI + ECU, at least $1200. Not cheap for the gains(or the estimated ones at least). Guess you gotta pay if you want to play.

 

with time we have learned a lot more about this vi.

things that i have noticed

1- its great for HIGH speed racing i.e. speeds above say 70mph

2- autos really can take advantage of the this mod (kinda sorta i think)

3- boost replaces the midrange hp loss

4- in a coincidence the g-force/jwt ecu + vi is a complimenting combo >>>> 96sleeper

5- if your a 5spd fully modded na guy you need not to worry about losing any races against someone who has the vi

6- with the vi cover installed on nigels turbo motor it looked sweet!

......

 

I don't think the G-force ECU gives a raised rev limiter?? Only the JWT.

 

At freeway speeds there is no contest, from 80+ an MEVI car will leave a non MEVI car pretty badly.

 

has JWT come out with a ECU for later 4 gen models? I know that you can put a 95-96 in the 97-99 but it trips the ecu, I thought they were in development...

 

later 4g's are screwed in the rear until JWT finally decides to pan out the 98-99 ECU's. And then there are the CA-spec cars from 99...they will probably be the most screwed.

 

This is very important to remember. This is why high RPM power results in a faster car on the street than low RPM power. The big gains at high RPM let take advantage of gearing.

 

awesome write up neal .... i don't think i want a MEVI as bad as i did before

 

I am waiting also for them.....

 

Although you did point out the benefits of a higher redline, you will still see gains without it. In all fairness to the MEVI and US, you are comparing two different rpm levels. You are taking the 4k-5.8k rang from the us manifold (it's strongest performance) and comparing it to the 4.35k-6.3k range of the MEVI (it's strongest performance). You need to consider the entire rpm band to effectively predict a cars performance. Remember, the VQ with a US manifold falls on its face after 5.8k, hard. That's still another .5k that it has to rev through, and it takes greater time to reach the next rpm than it did the rpm before.

The thing that would be better to compare is the gain vs loss durring weaker rpm ranges. Since the MEVI loses power durring the low-midrange, it might be best to calculate just how much is losed during that range, yet how much is gained over the US through the highest RPM range.

 

Nice write-up, Neal!

A picture is worth a thousand words. You wrote 661 according to MS Word

 

Thanks Steve! I don't know what to make of it, though...lol

 

good write up Nealoc187. Your results seem similar to the results of my data.

Frenzy based on my data, US manifold showed higher HP in just about every point along the curve in the lower rpm ranges (2100~5K) until the VI kicked in and the US fell dropped off dramatically.

i'll post pics of my dynoplots that compare the MEVI vs US manifold. the results are very close to the dyno pics posted by Steve..

 

The USIM (US OEM) has more power than the MEVI below 5500rpm
The MEVI only makes more power than the USIM below 5500rpm.

The problem is as follows. The revs drop significantly during the first three gears, and 31% on the 2-3 shift. If you shift the MEVI car at redline, you're still dropping back to the low-4000rpm's where the USIM is still making more power. What you gain with the MEVI is lost as soon as you shift gears, because you're right back in the range where the USIM has MORE power than the MEVI does.


This is where an ECU with a 7000rpm limiter comes into play.


With another 500rpm to play with, now the MEVI car could land the shifts at about 4800rpm, instead of the low-4000's. At this point the curves are already about to cross where the MEVI is making more power. So with more RPM to utilize, you're not stuck in the lower rev ranges as long where the MEVI gives less power.

The higher the rev-ceiling, the higher your shift points, which will keep the engine centered in the powerband most effectively.


This is the problem with engines that don't make their peak power until redline. You can't utilize all of the power fully. For maximum performance, you want to keep the revs centered around the point of peak power. But if you start hitting the rev limiter as soon as the engine peaks, there's no way to keep the revs centered around that point. The 00-01 Maxima guys have the same problem.

 

the torque is lower.. but the torque curve is flatter.. isn't a flatter torque curve what someone would be looking for?

 

The MEVI torque curve is flatter, but LOWER overall.

If the MEVI torque curve was at the same level as the USIM at 2000-5000rpm, AND also flatter, then that would be optimal. But some tradeoffs had to be made in the manifold design, trading some resonance (power) for better overall flatness.

You can't always have your cake and eat it too

 

Didn't I go over all this stuff about 3 month ago Of course I didn't use all the calculations though.

This is what I've seen on the dyno and at the track. On the dyno, my peak power went from 183fwhp@5400rpms/193fwtq@4500rpms to 189fwhp@6000rpms/186fwtq@4800rpms. I did loose a bit of power from 2500-4800rpms. Depending on where on the graph you're looking, I lost between 4-12fwhp/fwtq. Pretty much the MEVI smoothed out my power curves from 2000 all the way to 6400rpms. It lopped off the funky power curve "hills" in the midrange (which is where I lost the power). According to MY plots (yours may differ), with a 4800rpm switchover, there was a significant loss in power until 5500rpms when the MEVI finally overcame the USIM. With a 5000rpm switchover, the power curve was smooth, but still didn't overcome the power of the USIM until 5400rpms. I've studied my dynoplots religiously and it's apparent to me that if I would have delayed my switchover until 5300-5400rpms, my power curves with the MEVI would match the USIM from 4800-5400rpms and then after that it would exceed the USIM. My switchover is now set 5300rpms. Mardigras saw the same thing in his plots.

In the midrange, the car feels less "punchy" with the MEVI. Everything about the power delivery is smooth, but I do miss that slight turbo-like surge in power I had from 3500-4000rpms with the USIM, but the gain in topend power with MEVI is a good trade off.

On the track, the MEVI proved to perform the same as the USIM. Unfortunately, it took me until the last track day of the year to finally have the MEVI tuned right. At first, I was running a relay which was screwing up the switchover (rarely worked). Then I had my switchover set too low (4800rpms). Finally on the last day of the season, I pretty much had everything set right (5000rpm switchover, still a little low) and I ended up running a 14.70@96.9mph with a 2.28 60' which is the second best run I've ever had in this car.

Just like others have said, having a raised redline will really wake the MEVI up. The low entry RPMs on the 1-2 and 2-3 shifts don't work well with the MEVI. A 7000rpm fuel cut would help things and a 7300rpm redline would make things nearly ideal, but I don't think the valve train is up to the task. In gears 4th and 5th, the MEVI would literally run away from the USIM. A redline shift into 4th will land at ~5000rpms which is well above the MEVI loss in power.

I wish there was something we could do to raise the fuel cut instead of spending $550 on an ECU.

I don't know if it's in my head (others have reported it too), but running a 2000+ muffler really does seem to help things, especially with the MEVI. I swear I've gained back a lot of my midrange punch with this muffler and possibly even more topend power. Not only does the car sound a lot better, there might actually be some real-world gains associated with this muffler.


Dave

 

I was hoping you would post your experiences. thanks Dave. mo data is mo better!

I bet you're right about the 2000+ muffler. I've read about some members increasing the opening (from the b-pipe) to the muffler to 2.25 in diameter.

I wonder about the 5300 swithover point though. Because with a switch at 5200, my data shows that I didn't realize any power gains (vs USIM)until 5700. Did you notice any delay or did your dynos show power immediately at 5300?

 

Well, not really though. When you are racing you are going for optimal performance, that's why we shift before redline with the USIM. I started doing my comparison from 4500 to redline for both, and then I realized that with the USIM we don't run the car out to redline, we run it to about 6000rpm. Running it out to redline would skew the results severely in favor of the MEVI.

The rest of the RPM range is still there, but rarely used in a racing situation if you are doing things right, except in 1st gear. In 1st gear you are spinning the tires anyhow, so it doesn't matter how much power you are putting down at 3000rpm, you're just spinning and wasting that power anyways.

Were one so inclined, it would be possible to model an entire drag race with these calculations, the RPM drop in every gear, time to distance, etc. Or we could just have car test do it for us

 

Personally, I don't see the point in expanding the 2000+ muffler inlet to 2.25" because the internals of the muffler are still only ~2.0".

Take a look at my dyno plots before and after the MEVI:

http://www.cardomain.com/member_page...=259675&page=3

I know it's a bit hard to read, but the blue and purple lines are the MEVI numbers. As you can see, the switchover occurs at 5000rpms and power drops from 5000-5500rpms compared to the USIM. BUT, look what was happening from nearly 4800-5000rpms. The USIM and MEVI graphs were aligning themselves. If I would have delayed my switchover for another 300-400rpms, there would have been no drop in power from 4800rpms on.

For those that think these MEVI losses are significant, take a hard look at the graph. Only from 3300-3600rpms and from 4200-4600rpms do the losses occur. It's not like you're loosing a ton of power from 3100-4600rpms. You're only loosing a couple "hills".


Dave

 

The "hills" you're talking about are worth 10 wtq, which is significant. And it's still total power under the curve that you are losing in these RPM ranges.

FYI, I have a bigger version of your dyno on my site:

http://mywebpages.comcast.net/stevte...DaveB_MEVI.jpg

 

I just ran a CarTest of the USIM dyno and the MEVI dyno. Unfortunately my host is screwed up right now, but here's the summary.

The USIM if faster up to about 80 mph. After that the MEVI is gaining ground. The two cars are nearly dead-even at the 1/4 mile line, but the MEVI is going 2 mph and passing. After that the MEVI slowly walks away on the highway.

But wait, there's more.

Street Start: 5-60 mph: the USIM is faster.

But wait, there's more

Passing Times: 30-50mph
2nd: USIM
3rd: USIM
4th: USIM
5th: USIM

Passing Times 50-70 mph
3rd: USIM
4th: USIM
5th: USIM

Passing Times: 70-90 mph
3rd: MEVI
4th: USIM
5th: USIM

The USIM Maxima kicks the MEVI's butt in every single passing test except for the 70-90 mph in 3rd gear, which is really defining of the MEVI. The MEVI works best if what you want is all-out highway power. The 4th Gen is an urban beast with tons of low/mid-range for awesome around town performance, as seen by the lower speed passing tests. There are passes you could make in higher gears with the USIM that would require a downshift with the MEVI. But if highway power is what you want, the MEVI is definitely for you.

In deciding if this mod is for you, it's up to you to decide how you want your Maxima to perform best. This is my daily driver, and I do a lot of urban style cut-n-thrust driving (DC area) where 99.99999% of the time there's no chance in hell I'll ever make it above 80mph. So an MEVI is pretty much useless to me. I want to keep my Max tuned for maximum low/mid-range power to keep those better passing times.

If I lived in a much more rural area with lots of clear and unpatrolled highway to really open it up on, my opinion would probably be different about the MEVI. My opinion would also be different if my goal was all-out track performance on boost or all-out dyno king numbers.

It's just a question of what you want and how you want your Maxima to perform the best.

If you want an "urban racer" with best performance at lower speeds, it's probably best to stick with the USIM. If what you want is a "highway beast", then the MEVI is your ticket.

Bottom line: choose what's best for you and your style

 

Did I say this after looking at Jane's dyno compared to my dyno about... a year ago?

 

For me, I am in between and I'd like to get extra power on low ends as well as on the high end. I think when I get the y-pipe on the car that should bring back what I lose on the low end so the feel should be the same as with the USIM. Bags claims that he felt no loss and maybe its because of the Y-pipe and other goodies he has on the car. He's also dropping a lot of HP (as well as 96sleeper) for an auto.

I am 99.999999999% that this thing is going on this spring but the more we talk about this it seems the more I learn. Hell, with the few guys that took a chance on the VI, they were able to prove that we have the mod to make high end power. Hopefully soon we'll be tring to find something to give us the low end back.

 

Yeah, a few mods like intake and y-pipe should take care of any losses in the low/mid-range that you get with the MEVI. The MEVI is definitely something to get after you've got pretty much everything else, and not before.

 

Yes

And because j0o are so smart, that is why you now own .orgy

 

after reading this post, it's very hard to justify buying a variable intake manifold for myself. i was able to hit a trap speed of 98.5mph on my stock manifold. the cost is just too great for a minimal amount of hp gain at such a narrow rpm band. if you just wanna stretch the limits of the stock motor, you don't need a variable manifold (to run 13's). i was 2 hundreths away from an all motor 14 flat. the only reason i didn't reach that or possibly greater was i hit a low fuel cutoff when my engine stalled at 4,000rpm in 4th gear. i spend nearly 2 seconds in 4th gear by the end of the 1/4mi. i coasted through the line and still got a 14.11. for the money, get slicks instead! my money is going to my S13 though. so i might not reach 13's anytime soon.

 

Here's a picture of my dyno numbers. This isn't an ideal comparison to SteVTEC's picture since the x axis have different scales, but at least people can see what all the calculations show. I'll do a more detailed plot--probably with the x axis in increments of 100 RPM-- that should show sufficient detail.


BLUE is the USIM + modz
RED is the MEVI + modz

 

I really wish that we had some consistant data for the VI. When I had my VI with hybrid dynoed I didn't lose any low-end. I gained hp or equaled the USIM from 2100 to 3200 rpms. My midrange was what got whacked, especially between 4k and 5200 rpm.

Needless to say I'm saving my pennies for JWT ECU.

 

J_bryan I'd be curious to know if your car might dyno better w/ the stock ECU rather than the Gforce. I'm trying to figure out why your dyno may be different from speedtrips. I think you both had hybrid intakes as well as y pipes. Maybe speedtrip had a b pipe at the time?? Just trying to figure out the differences. I can't wait to get mine dynoed on the 2nd.

 

too .... much .... info .....
brain .... freezing .... ahhhhhhh


good info everyone, much food for thought

 

Toolrocks and I were discussing this a bit and it looks there may be a reason why my dynos seem to lose more HP than speedtrip and daveb in the midrange. Could it be that the G-force ECU does not work optimally with the MEVI??

Take a look at these Air fuel curves..It looks like I'm running rich in the midrange (between 3K and 4K). This richness correlates with the RPM where the USIM is ahead of the MEVI...Could the G-force be causing this?? Another thing I noticed is that I think I'm burning more gas now than without the MEVI. If I'm running rich then that might support the idea that the G-force (at least my G-force) may not work optimally with the MEVI and subsequently burning more gas.

I'm no expert on reading air/fuel ratios so someone correct me if I have it backwards.

sorry but this pic is big too..

BLUE is the USIM + modz
RED is the MEVI + modz

 

I don't think 10wtq/10whp spread over two areas that only last 400rpms is significant, but that's just me.

Your "passing time" comparison test is very informative, but a few fractions of a second in passing time really doesn't concern me. I'm more interested in the all out performance. On the highway, this thing is a blast. It really is fun to wind out the VQ straight to redline. The extra smoothness of the motor with the MEVI is great and the sound of the motor is so much more refined. My car spends a lot more time above 5000rpms and it's plenty happy to do it. Things are even better with the 2k+ muffler. Hopefully a JWT ECU will be in my future soon so I can take full advantage of this thing.


Dave

 

ah i dont get this **** = / if ure at a dragstrip ure launching at high RPMs so u will be in the lower part when u first first start but soon u will be in the higher part where the MEVI is, and if u have an underdrive pulley it will also help you get into the powerband quicker, and if u have an ecu and ure shifting at about 7 grand with a short throw shifter ure car wont drop to much less then 5000rpms and at that point ure supposed to have like another 25hp? shoulndt this help ure quarter mile times not just ure 70+mph highway driving? i udnerstand it would be useless if ure just cruising around at lower rpms, but u can just always drop it a gear if ure cruising at like 45 and have ure rpms after 5 and should give u the boost shouldnt it? please explain (PM with an answer me cuz i will prolly forget to find this thread again ) haha

 

Dude, talk about bringing a thread back from the dead!

 

Are there any pics?

This is a very old thread...

Where can I see pisc of MEVI, 00VI and USIM compared?